This invention relates to fuel compositions for internal combustion engines and more particularly to fuel compositions which are characterized as being either unleaded or low lead fuels.
With the removal of lead additives such as, for example, tetraethyl lead and tetramethyl lead, from gasoline in order to reduce air pollution, it was discovered that the lead within the fuel had several desirable properties. It was found, for example, that the lead not only acted as an anti-knock agent, but was also effective in contributing toward the prevention of valve seat recession. In the conventional internal combustion gasoline engines, the exhaust valves generally seat against their valve seats with a slight rotary motion. This rotary motion is imparted to the valve stem during its operation to shift the relative position of the valve and to prevent uneven wear on the valve tip. The rotary motion also causes the valve to sit in different positions on each operation. With the elimination of the lead additives from gasoline, it has been found that a drastic increase in wear of the valve seat occurs. For example, see "Unleaded Versus Leaded Fuel Results in Laboratory Engine Tests", E. J. Fuchs, The Lubrizol Corporation, presented at the Society of Automotive Engineers National West Coast meeting, Vancouver, British Columbia, Canada, Aug. 16-19, 1971 (32 pages).
Valve seat wear is a function of engine design, load and speed conditions, and valve operating temperature. Valve seat wear is most severe under high speed and high load conditions. The problem of valve seat wear is observed in tractors, automobiles operated at high velocity, inboard and outboard motors, etc., especially when the internal combustion engines were designed primarily for leaded fuels.
U.S. Pat. No. 2,764,548 describes motor oils and motor fuels containing various salts of dinonyl-naphthalene sulfonic acid including the sodium, potassium, calcium, barium, ammonium and amine salts. The salts are reported to be effective rust inhibitors.
U.S. Pat. No. 3,506,416 describes leaded gasolines containing gasoline soluble salts of a hydroxamic acid RC(O)NHOH where R is a hydrocarbon group containing up to 30 carbon atoms. The metal may be selected from the Group Ia, IIa, IIIa, Va, Ib, IIb, IIIb, IVb, Vb, VIb, VIIb, VIII and tin.
U.S. Pat. No. 3,182,019 describes lubricating and fuel oils including complexes containing an alkali or alkaline earth metal carbonate in colloidal form.
The use of sodium in lead-free gasoline compositions for inhibiting valve seat recession is suggested in U.S. Pat. No. 3,955,938. The sodium may be incorporated into the fuel in a number of different forms such as sodium derivatives or organic compounds which are soluble, or dispersed in the gasoline. For example, simple sodium salts of an organic acid such as sodium petroleum sulfonate can be utilized although the sodium preferentially is added in the form of a sodium salt of an inorganic acid such as sodium carbonate in a colloidal dispersion in oil. Other convenient forms for introducing sodium into the fuel which are described in U.S. Pat. No. 3,955,938 include various sodium salts of sulfonic acids, sodium salts of saturated and unsaturated carboxylic acids, sodium salts of phosphosulfurized hydrocarbons such as may be prepared by reacting P.sub.2 S.sub.5 with petroleum fractions such as bright stock, and sodium salt of phenols and alkylphenols. The amount of sodium additive included in the fuel is an amount to provide from about 0.5 to 20, preferably 0.5 to 10 lbs. of sodium per 1000 barrels of gasoline.
It also has been suggested in the prior art that gasoline compositions can be improved by including certain detergents and dispersants. U.S. Pat. No. 3,443,918 describes the addition to gasoline of mono-, bis- or tris-alkenyl succinimides of a bis- or tris-polymethylene polyamine. These additives are reported to minimize harmful deposit formation when the fuels are used in internal combustion engines.
U.S. Pat. Nos. 3,172,892, 3,219,666, 3,272,746, 3,281,428 and 3,444,170 to Norman et al issued May 13, 1969 are directed to polyalkenyl succinic type ashless additives, and the '386 patent teaches the use of the additive disclosed therein as a fuel detergent. U.S. Pat. No. 3,347,645 also describes the use of alkenyl succinimides as dispersants in gasoline, but it is there noted that the dispersants promote aqueous emulsion formation during storage and shipping. U.S. Pat. No. 3,649,229 teaches a fuel containing a detergent amount of a Mannich base prepared using, among other reactants, an alkenyl succinic compound. U.S. Pat. No. 4,240,803 also relates to hydrocarbon fuel compositions containing a detergent amount of a specific alkenyl succinimide wherein the alkenyl group is derived from a mixture of C.sub.16-28 olefins.
Although sodium salts of organic acids have been suggested as being useful additives in gasoline, and in particular, low lead or unleaded gasolines, such sodium salts have a tendency to emulsify water into gasoline, and with some sodium salts an undesirable extraction of the sodium into the water occurs.